In recent years, as an illumination apparatus replacing an incandescent lamp or a fluorescent lamp, an organic EL module has been receiving attention and many studies have been conducted. Here, an organic EL module refers to a thin organic EL tile that emits light in a planar manner and is housed in a housing such as a bezel (a case, a frame). The terms such as an organic EL tile or panel as used herein are defined in International Standard IEC62868.
An organic EL tile is obtained by forming an organic EL element on a substrate such as a glass substrate or a substrate formed by a transparent resin film/metal sheet. The organic EL element is made up of a pair of electrodes one or both of which are light pervious and oppose to each other, and functional layers (light-emitting functional layers) laminated between the pair of electrodes.
In many cases, an organic EL tile is sealed with a sealing glass cap having a recess, or a sealing film such as an inorganic insulating film of Sift or SiN deposited on the organic EL element, or an organic insulating film such as an acrylic insulating film.
When power is applied across the electrodes of an organic EL element, electrically excited electrons and holes are recombined with each other in the organic EL element, allowing the organic EL tile to emit light. That is, an organic EL tile is a device characterized in being thin, lightweight, and emitting light in a planar manner.
A planar light-emitting tile also refers to, in addition to the above-described organic EL tile, an LED tile which is obtained by arranging LEDs in a planar manner or combining an LED and a diffusing plate. That is, a planar light-emitting tile generally refers to a planar light-emitting member, including the organic EL tile.
In order for a planar light-emitting tile represented by an organic EL tile to be used as an illumination device, a power supply circuit and power supply lines for connecting the electrodes of the planar light-emitting tile and any external power supply are necessary. In some cases, a printed circuit board (PCB) such as an FPC (flexible printed circuit) or an RPC (rigid printed circuit) is used as the power supply circuit or the power supply lines.
Further, as described above, an organic EL tile has a substrate such as a glass substrate. Therefore, it is necessary to prevent any break or crack of the substrate, and any injury to the user's finger touching the end part (edge) of the substrate.
Accordingly, in some cases, an organic EL tile and a housing are combined to each other as a module, and introduced in this state to the market as an illumination device.
That is, any housing (casing) is provided to an organic EL tile, and combined with each other as an organic EL module. In this state, the organic EL module is introduced to the market as an illumination device.
Meanwhile, an illumination device structured by a light-emitting module such as the combined organic EL module or the like cannot provide any novel and effective value to the world if it fails to fully exhibit the characteristics of the planar light-emitting tile such as an organic EL tile, that is, being thin, lightweight, emitting light in a planar manner and the like.
Further, in order to improve the light-emitting efficiency, lifetime, and reliability of a combined light-emitting module, heat dissipation or soaking must be promoted. With an LED tile that attains high temperatures in emitting light, the heat problem is significant and heat dissipation or soaking must be achieved.
As method and structure for providing a casing, Patent Document 1 discloses a scheme of holding an organic EL tile with a frame having a flange. The scheme is intended to achieve a reduction in thickness with a simple structure.
Patent Document 2 discloses a scheme of reducing a heat emission amount by providing a second electrode that is in contact with one of electrodes provided on opposite sides of a thin film organic light-emitting layer of an organic EL tile.
Patent Document 3 discloses a structure in which elongated organic EL modules are disposed in parallel in the longitudinal direction.